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Biology A Level > :) Cell Division And Cellular.Organisms > Flashcards

:) Cell Division And Cellular.Organisms Flashcards

1
Q

What are the stages of the cell cycle?

A 
Synthesis 
Gap phase 1
G1 checkpoint 
M phase 
Gap phase 2
G2 checkpoint 
Synthesis
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2
Q

G2 checkpoint

A

Cell checks whether all DNA has been replicated without any damage
If it had the cell can enter mitosis

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3
Q

M phase

A

Mitosis (nuclear division) and cytokinesis

(Cytoplasmic division) Metaphase checkpoint

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4
Q

Gap phase 1

A

Cell grows and new organelles and proteins are made

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5
Q

G1 checkpoint

A

Cell checks that the chemicals needed for replication are present and for any damage to the DNA before entering S-phase

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6
Q

Gap phase 2

A

Cell keeps growing and proteins needed for cell division are made

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7
Q

Synthesis

A

Cell replicated its DNA ready to divide by mitosis

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8
Q

When does the cell cycle start and end?

A

Starts When a cell has been produced by cell division

Ends with cell dividing to produce two identical cell

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9
Q

What does the cell cycle consist of?

A

Period of cell growth and DNA replication (interphase)

Periods of cell division (M phase)

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10
Q

What is interphase subdivided into?

A

Cell growth
Subdivided into three different separate growth stages
G1, s and G2

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11
Q

How is the cell cycle regulated?

A

By checkpoints that occur at key points during a cycle to make sure it’s okay for the process to continue

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12
Q

What is mitosis needed for?

A

The growth of multicellular organisms (like us)
Repairing damaged tissues
Method of asexual reproduction for some plants, animals and fungi

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13
Q

What is mitosis really?

A

One continuous process

Series of division phases: prophase, metaphase, anaphase and telophase

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14
Q

When does interphase happen?

A

Before mitosis in the fell cycle

When the cell grows and replicates their DNA ready for division

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15
Q

Describe interphase

A

Cell carried out normal functions and prepares to divide
Cells DNA is unraveled and replicated to double its genetic content
Organelles replicated so it has spare ones
ATP is increased (ATP provides energy needed for cell division)

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16
Q

Describe prophase?

A

Chromosomes condense getting shorter and fatter
Tiny bundled of protein (centrioles) start moving to opposite ends of cell forming network of protein fibres (spindle)
Nuclear envelope breaks down and chromosomes lie free in the cytoplasm

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17
Q

What is the cell cycle? The

A

The process that all body cells in multicellular organisms use to grow and divide

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18
Q

What are the chromosomes made of when mitosis begins?

A

Two strands joined in the middle by a centromere. The separate strands are called chromatids

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19
Q

Why are there two strands?

A

Each chromosome has already made an indentical copy of itself during interphase. When mitosis is over, chromatids, end up as one-strand chromosome in the new daughter cells

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20
Q

Describe metaphase

A

Chromosomes (each with two chromatids) line up along the middle of the cell and become attached to the spindle by their centromere.

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21
Q

What happens at the metaphase checkpoint

A

The cell checks that all the chromosomes are attached to the spindle before mitosis can continue

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22
Q

Anaphase describe

A

Centromeres divide separating each pair of sister chromatids. The spindle contracts, pulling chromatids to opposite ends of the cell, centromere first.

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23
Q

Telophase

A

Chromatids reach opposite poles in the spindle. They uncoil and become long and thin again. Called chromosomes again. Nuclear envelope forms around each group of chromosomes so there are two nuclei

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24
Q

Cytokinesis

A

Cytoplasm divides in animal cells a cleavage furrow forms to divide the cell membrane. There are now two daughter cells that are genetically identical to the original cell to each other. Cytokinesis usually begins in anaphase and ends in telophase.
Separate process to mitosis

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25
How can you observe the cell cycle?
Stain chromosomes | So you can see under microscope meaning you can watch what happens during mitosis.
26
How do you recognise cells in interphase?
The chromosomes will be spread out and not condensed
27
Meiosis produces what?
Gametes for sexual reproduction
28
What happens in sexual reproduction?
Two gametes join together at fertilisation to form a zygote. Zygote then divides and develops into a new organisms
29
What type of cell division is meiosis?
One that happens in the reproductive organs to produce gametes
30
What does meiosis involve?
A reduction division Cells that divide by mitosis produce full number of chromosomes to start with but cells that are found that are formed from meiosis have half the number. Cells with half the normal number of chromosomes (haploid cells)
31
What are cells formed by meiosis?
Genetically different because each new cell ends up with a different combination of chromosomes
32
Why is meiosis so important?
Without meiosis, the number of chromosomes double when the gametes fused.
33
What does mitosis involve in terms of divisions?
Meiosis 1 and meiosis 2
34
What is meiosis 1?
A reduction division
35
What are meiosis I and meiosis II split up into?
Prophase Metaphase Anaphase Telophase
36
What does meiosis begin with?
Interphase | During interphase, DNA unraveled and replicates to produce double-armed chromosomes called sister chromatids
37
Prophase I
Chromosomes condense getting shorter and fatter Chromosomes arrange themselves into homologous pairs and crossing-over occurs. Like in mitosis, centrioles start moving to opposite ends of the cell forming the spindle fibres. Nuclear envelope breaks down
38
Metaphase I
Homologous pairs line up across the centre of the cell and attach to the spindle fibres by their centromeres
39
Anaphase I?
Spindles contract separating homologous pairs- one chromosomes goes to each end of the cell
40
Telophase I?
Nuclear envelope forms around each group of chromosomes
41
Cytokinesis?
Division of cytoplasm occurs and two haploid daughter cells are produced
42
Humans chromosome number?
46 chromosomes | 23 pairs
43
Where did the two chromosomes come from?
One chromosome in each pair came from mum and one from dad.
44
What are the chromosomes that make up each pair?
Same size Same genes (can be different alleles) Called homologous pairs
45
What happens after Meiosis I?
Meiosis II | Two daughter cells undergo prophase II, metaphase II, anaphase II, telophase II, cytokinesis (a lot like mitosis)
46
Anaphase II?
Pairs of sister chromatids are separated each new daughter cell inherits one chromatid from each chromosome. Four genetically different haploid daughter cells are produced. These are gametes
47
When does chromosome cross over in meiosis happen?
During prophase I of meiosis I, homologous pairs of chromosomes vine together and pair up. Chromatids twist around each other and bits of chromatids swap over. The chromatids still contain the same genes but now have different combinations of alleles
48
Two main events leading to genetic diversity?
Crossing over of chromatids | Independent assortment of chromosomes
49
Crossing over of chromatids
Happens in meiosis I | Means each of the four daughter cells formed from meiosis contain chromatids with different alleles
50
What is each homologous pair of chromosomes in your cell made of?
One chromosome from maternal and one chromosome from paternal
51
When do homologous pairs line up?
Metaphase I
52
When do homologous pairs separate?
Anaphase I
53
What happens as a result of this?
It's completely random which chromosome from each pair ends up in which daughter cell
54
What do the four daughter cells produced by meiosis have?
Completely different combinations of those maternal and paternal chromosomes
55
What is this process called?
Independent assortment of the chromosomes
56
What does this shuffling of chromosomes lead to?
Genetic variation in any potential offspring
57
What are multicellular organisms made of?
Many different cell types that are specialised for their function e.g. Liver cells, muscle cells, white blood cells
58
What did all these specialised cell types originally come from?
Stem cells
59
Stem cells are?
Unspecialised cells | Can develop into different types of cells
60
Who has some sort of form of stem cells?
All multicellular organisms
61
When are stem cells found in humans?
Early embryos and in a few places in adults. Stem cells in early embryos can develop into any type of human cell. Adult stem cells can only develop into a limited range of cells
62
How do stem cells specialise?
Divide to form new cells via Differentation
63
What are adult stems cell used for in animals?
Replace damaged cells e.g. Make new skin or blood cells
64
What are stem cells needed for in plants?
To make new shoots and roots throughout their stem cells because they are always growing
65
What can stem cells in plants differentiate?
Various plant tissues including xylem and phloem
66
What else can a stem cell do?
Divide to produce more undifferentiated stem cells e.g. Can renew themselves
67
What do cells in the bone marrow do?
Differentate into blood cells
68
What are bones?
Living organs containing nerves and blood vessels main bones of the body have narrow in the centres
69
What do adult stem cell do here?
Divide and differentiated to replace worn out erythrocytes and neutrophils
70
Cell in meristem
Stem cells found in meristem | In root and stem cells of vascular cambium divide and differentiate to become xylem and phloem sieve tubes
71
What could stem cells be used for?
Replace damaged tissue in a range of conditions e.g. Might be possible to use stem cells to treat neurological disorders like Alzheimer's and Parkinson's
72
How can stem cells help Alzheimer's?
Nerve cells in the brain die in increasing numbers resulting in severe memory loss. Researchers are hoping to use stem cells to regrow healthy nerve cells in people with Alzheimer's
73
How can stem cells treat Parkinson's?
Suffer from tremors that they can't control. The disease causes the loss of a particular nerve cell found in the brain needed to control movement. Transplanted stem cells may help regenerate the dopamine-producing cells
74
What else can stem cells be used for?
By scientists researching developmental biology how organism grow and develop Studying stem cells can help us to understand more about things like developmental disorders and cancer
75
What happens when cells differentiate?
They have a specific function | Structure is adapted to perform that function
76
Describe neutrophil
Type of white blood cells Defends body against disease Flexible shape allows them to engulf foreign particles or pathogens. Many lyposijes in their cytoplasm contain digestive enzymes to break down engulfed particles
77
Erythrocytes
Carry oxygen in blood | Biconcave disc shape provides a large surface area for gas exchange. Have no nucleus so more room for haemoglobin
78
Epithelial cells
Cover surface of organs Cells joined by interlinking cell membranes and a membrane at their base. Ciliated epithelia have cilia that beat to move particles away. Squamous epithelia are very thin to allow efficient diffusion of gases
79
Sperm cell
Flagellum so can swim to egg Have microchrondria to provide energy to swim Acrosome contains digestive enzymes to enable sketch to penetrate surface of egg
80
Palisade mesophyll cell
In leaves Do most of photosynthesis Contain many chloroplasts so absorb a lot of sunlight. Thin walls so carbon dioxide can easily diffuse into the cell.
81
Root hair cell
Absorb water and minerals ions from soil Large surface area for absorption and a thin permeable cell wall for entry for water and ions. The cytoplasm contains extra mitochondria to provide the energy needed for active transport
82
Guard cells
Found in pairs with a gap between them to form a stoma One of the tiny pores in the surface of the leaf used for gas exchange In light, guard cells take up water and become turgid Thin outer walls and thickened inner walls force them to bend outwards opening the stoma allowing leaf to exchange gases for photosynthesis
83
What's a tissue?
A group of cells plus ant extracellular material secreted by them that are specialised to work together to carry out a particular function. A tissue can contain more than one type of cell
84
Squamous epithelium
Single layer of flat cells lining a surface | Found in many places including alveoli in the lungs
85
Ciliated epithelium
Layer of cells covered in cilia Found on surface where things need to be moved In the trachea for instance where cilia waft mucus along
86
Muscle tissue
Made up of bundles of elongated cells called muscle fibres Three different types of muscle tissue: smooth (found lining the stomach wall), cardiac (found in the heart), skeletal (used to move) all slightly different in structure
87
Cartilage
Type of connective tissue found in the joints Shapes and supports the ears, nose and windpipe Formed when cells called chondroblasts secrete an extracellular matrix (jelly-like substance containing protein fibres) which become trapped inside
88
Xylem tissue
Transports water around plant Supports plant Contains hollow xylem vessel cells which are dead and living parenchyma cells Perforated by pits Parenchyma cell fills in gaps between vessels
89
Phloem tissue
Transport sugars around plant Arranged in tubes Made of sieve cells, companion cells and some ordinary plant cells
90
Sieve cell
Has end walls with holes in so sap can move easily through them. End walls called sieve plates
91
Organ
Group of different tissues that with together to perform a particular function
92
Lungs
Contain squamous epithelial tissue in the alveoli Ciliated epithelial tissue in the bronchi Have elastic connective tissue and vascular tissue in the blood vessels
93
Leaves
Contain palisade tissue for photosynthesis as well as epidermal tissue to prevent loss from the leaf Xylem and phloem tissues in the veins
94
What do organs work to form?
Organ systems- each system had particular function
95
Respiratory system
Made of all organs, tissue and cells involved in breathing | Lungs, trachea, larynx, nose, mouth and diaphragm are all part of the respiratory system
96
Circulatory system
Made up of organs involved in blood supply | Heart, arteries, veins and capillaries

Biology A Level (26 decks)

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